Split Screen on a Mac Without Touching the Green Button: The Rectangle Way

macOS still doesn't make side-by-side windows easy. The green button drops you into Split View, a separate full-screen Space where the menu bar hides and Cmd+Tab starts acting weird. Rectangle, a free open source utility, fixes this with two keystrokes: Ctrl+Option+Left sends a window to the left half of the screen, Ctrl+Option+Right sends the next one to the right. Done. Both windows stay normal windows on your normal desktop.

Here's how to set it up and what it can do beyond basic halves.

Setup takes about three minutes

Download the app from rectangleapp.com, or install it with Homebrew if that's your style: brew install --cask rectangle. It runs on macOS 10.15 and newer, Intel and Apple Silicon both.

On first launch, macOS will ask you to grant Accessibility permission in System Settings, under Privacy & Security. Don't skip this. Rectangle moves other apps' windows, and the system requires that permission for any app that does. Nine out of ten "Rectangle isn't working" complaints trace back to this single checkbox, usually after a macOS update quietly resets it.

The app then offers two shortcut presets: its own defaults or the old Spectacle bindings, for people migrating from that discontinued app. If you're new to both, take the Rectangle defaults.

The shortcuts that matter

Ctrl+Option plus an arrow key covers the basics. Left and Right give you the classic split. Up and Down stack two windows vertically, which is surprisingly useful on a portrait monitor. Ctrl+Option+Enter maximizes the window, and this is worth pausing on: unlike the green button, it fills the screen without creating a full-screen Space. The window stays a window. After years of fighting macOS full-screen mode, this one shortcut alone justified the install for me.

Ctrl+Option+C centers a window without resizing it, handy for a video call or a document you want to read in a narrow column. Ctrl+Option+Backspace restores the previous size when you change your mind.

Thirds are where it gets good

Halves are fine on a 13-inch laptop. On a 27-inch display or anything wider, thirds are the layout you'll actually live in. Ctrl+Option+D, F, and G snap a window to the left, center, or right third. E and T give you two-thirds on either side.

My daily arrangement: code editor at two-thirds left, Slack pinned to the right third. The editor gets the space it needs, the chat stays visible without stealing focus. On an ultrawide, three full columns turn one monitor into three workstations.

There's a trick most people miss for weeks: press the same shortcut repeatedly and the window cycles through sizes on that edge. One press of Ctrl+Option+Left is a half, the second press is two-thirds, the third is one-third. One key combo, three layouts. Native macOS tiling still can't do this.

Prefer the mouse? Drag to an edge

Rectangle also does Windows-style snap areas. Drag a window toward the left edge of the screen and a translucent outline previews the left half. Drop it there. Corners give you quarters, the top edge maximizes. If you're coming from Windows 11, your muscle memory works on day one.

Shortcuts and snap areas stay active at the same time, so you don't have to choose. Individual zones can be switched off in preferences if a corner keeps catching windows by accident.

But macOS has tiling now, right?

Since Sequoia, yes, and for some people it's enough. Native tiling handles halves and quarters with drag-to-edge and a few fixed shortcuts. What it doesn't have: thirds, size cycling, a restore shortcut, a one-key way to throw a window to another monitor, or the ability to remap every binding to whatever you want. It also doesn't exist at all on anything older than macOS 15, while Rectangle reaches back to Catalina.

Honest advice: if halves cover everything you do, skip the install and use what Apple ships. The moment you want a third column or your own keybindings, you've outgrown it. Both can run at once, though I'd disable the native drag-tiling so you're working with one consistent set of snap zones.

Quick fixes for the common problems

Shortcuts dead after a system update: open System Settings, Privacy & Security, Accessibility. Remove Rectangle from the list entirely (the minus button, not the toggle), add it back, relaunch the app. Fixed.

One specific shortcut not responding while the rest work: another app owns that combination. IDEs like IntelliJ are frequent offenders with Ctrl+Option combos. Rebind on whichever side you use less.

A particular app refusing to resize: some apps enforce minimum window sizes or draw non-standard windows. That's the app, not Rectangle.

Is it safe, and what does it cost

Free, open source, code public on GitHub, maintained since 2019 as the successor to Spectacle. The Accessibility permission is the only access it requests. No account, no telemetry, no subscription. A paid sibling app, Rectangle Pro, adds custom sizes, per-app layouts, and settings sync across Macs, but nothing in this guide requires it.

Install it, set a couple of shortcuts into your fingers, and the green button becomes something you never think about again.